Apparatus for producing and modulating an ionic discharge



July 9,, 1935. 5, RUBEN 2,007,936

APPARATUS FOR PRODUCING AND MODULATING AN xomc DISCHARGE Filed July 31, 1930 2 Sheets-Sheet 1 BY. A ONEY July 9, 1935. s. RUBEN 2,007,93 APPARATUS FOR PRODUCING AND M ODULATIN G AN IONIC DISCHARGE Filed July 51, 1930 2 Sheets-Sheet 2 BY Z3 (2% 5;

'ITORNEY Patented July 9, 1935 PATENT OFFICE APPARATUS FOR PRODUCING AND MODU- LATING AN IONIC DISCHARGE Samuel Ruben, New Rochelle, N. Y., assignor to Sirian Lamp Company, Newark, N. J., a corporation of Delaware Application July 31, 1930, Serial No. 471,977

5 Claims. (01. 176-1) This invention relates to ionic discharge devices and particularly to such a device in which the discharge may be modulated so that it lends itself for use in producing modulated lighting eifects as in television, sound-on-film apparatus, signaling devices, or other devices using rapid changes in light intensity.

Heretofore for the production of modulated light, especially in devices having radiation in the acttinic part of the spectrum, a low pressure gas discharge between two electrodes has been employed requiring a high voltage to operate, modulation being accomplished by superimposing an audio frequency oscillation on the supply current leads. This type of discharge is limited in intensity due to localization effects which are common with high intensity arcs or low pressure discharges and require an elaborate equipment for the generation of the necessary high voltage discharge. i

It is therefore one of the objects of the present invention to produce an intense ionic discharge of such a character that it may be modulated without lag at the higher audio frequencies.

Another object of the invention is to provide a light capable of producing an intense ionic discharge at relatively low voltages.

Another object of the invention is to provide a system for modulating a high intensity discharge by relatively minute electrical variations.

Other objects of the invention and objects relating particularly to the method of manufacturing and assembling the various parts and to the circuits for using the device will be apparent as the description of the invention proceeds.

Several embodiments of the invention have been illustrated in the accompanying drawings in which:

Fig. 1 is a schematic showing of a system for producing an image on a screen for television and including a side elevational view of the lamp for producing the light;

Fig. 1a is an enlarged longitudinal sectional elevation of the electron emitting element;

Fig. 2 is a diagram .of a system for producing a sound wave on a sensitized moving picture film; and

Fig. 3 shows a circuit adapted for use in a visible signaling system.

Referring now more specifically to the drawings, one embodiment of the lamp of the invention is illustrated in Fig. 1 and comprises an envelope I0 having the usual press H formed integral with the envelope and upon which the elements of the lamp are mounted. A coil l2 of resistance wire is coated with an electron emitting material l3. The coil may be of any desired resistance material but preferably of a refractory metal such as tungsten to increase the light output of the lamp and the electron emitting mate- 5' rial may be the oxides of barium, strontium, calcium, magnesium, or any other material which tends to increase the emission of electrons from a body. The coil l2 may be supported at its lower end upon a short support rod l4 which is 10 sealed in the press ll while the upper end of the coil may be supported upon a rod l5 which may be bent outwardly and downwardly and may also be sealed in the press ll. Leading-in wires 16 and I 1 may be attached respectively to the rods l5 l5 and M to connect the filament in a suitable circuit. A support rod l8 may be mounted substantially parallel to the coil l2 and may be provided with a series of rings Ilia which extend around the coil l2 in spaced relation along the 20 length thereof and may be welded to the support I 8. The support I8 and rings Ilia. form the modulating grid l9. The support rod l8 may extend downwardly and may also be sealed in the press II and a leading-in wire 20 may be con- 25 nected to it as indicated.

The envelope I0 is filled with a suitable inert gas, preferably a monatomic gas such as neon, argon, helium, krypton, xenon, and the like or mixtures of these gases and also a low pressure 3 of metal vapor such as cazsium or mercury vapor may be added if desired, the pressure in the bulb being in the neighborhood of 200 mm. of mercury. This pressure of the gas in the bulb appears to depend somewhat upon the voltage used and high- 35 er pressures may be used if a higher voltage is contemplated. The pressure of the gas should be sufiicient in any case to restrict the ionic discharge when the filament is energized to the vicinity of the filament so that a halo of intense illumination is formed along the length of the filament and within a short distance of it.

Any desired number of filaments may be used in the lamp and these may be arranged in any desired shape or configuration although I have described and shown a single straight filament for purposes of convenience. Where it is desired to use the lamp on a llfl volt circuit, for instance, it may be preferable to have as many as four such filaments mounted in series and spaced about a common central axis.

Care should be taken in exhausting the lamp that all undesirable gases and vapors are removed from the envelope. The envelope with the press and elements mounted as indicated in the figure may be connected to an exhaust pump in the usual manner and an oven placed over it to raise the temperature thereof to between 350 to 400 C. or to as high a temperature as the glass will stand without softening. A current may be run through the filament at this time to heat it to a red heat at a temperature of about 600 C. and the heat and exhausting may be continued until there is no fluorescence when a hightension current from an induction coil is directed against the walls of the envelope or in other words until there is no more gas inside of the envelope. This process is continued until a high vacuum of about .5 micron is obtained. Current .is then increased through the filament until the temperature thereof is slowly raised to about 800 C. with a bright red color. This drives out the binder in the electron emitting material and other occluded gases which may be present.

When no more gas is found in the bulb, the oven may be raised and the filament heated to about 1200 C. or slightly less, the pump being connected all this time to maintain a high vacuum. The pump may then be shut off, the filament current turned ofi, and a slight amount of neon gas (about /2 mm.) may be admitted to the envelope and the filament current turned on again and gradually increased. Spots of localized discharge will then appear having a reddish color and these spots will gradually spread until a diffused glow completely fills the envelope. This process activates the electron emitting coating and is maintained until the discharge is uniform throughout the entire bulb which usually takes less than ten minutes when the activation is completed. During this time the current on the filament should not be raised too high so that the coating will not be destroyed or thrown off from the filament. If white discharge spots appear on the filament or support rod it is an indication that there are more gases and vapors in the bulb and the bulb should again be exhausted and thewhole process of activation'repeated. In the activating process the support rod 15 and other metal parts in the envelope as well "as parts of the fila- 'ment itself aid in the activation as they act as cooperating electrodes having a different potential than the potential of any given portion of the filament and coating.

When the activation is completed the filament temperature may be raised for a moment to about 1400 C. and then the vacuum pump may be again connected and the gas pumped out to remove any undesirable gases which have been thrown off during the activation process. The filament circuit may then be disconnected, the pump turned off, and the desired gases admitted into the envelope. In one instance a mixture of 50 mm. of neon and 150 mm. of argon were found to give good results. The bulb may then be sealed off after which a small quantity of magnesium which has been placed in a suitable container, as 41 mounted, for instance, on the support rod l5, may be flashed to absorb any impurities. The bulb may then be ready for use.

The metallic vapor may be introduced when the magnesium is flashed by providing a salt of the desired metal in the container with the magnesium. Thus if caesium chloride is placed in the container, caesium will be liberated leaving magnesium chloride which is a stable salt.

The leading-in wires 16 and IT for the coil 12 or filament of the lamp may be connected by means of the wires 2| and 22 respectively to a generator 23 for producing direct current for energization of the filament. A choke coil 24 may be included in the circuit of the wire 22 and condensers 25 and 26 may be connected across the leads 2| and 22 one at each side of the choke coil 24 in a manner well-known in the art to assist in smoothing out any variations caused by the generator. The modulating grid l9 may be connected by means of a wire 21, connected to the leadingin wire 20, to one end of the secondary 28 of a transformer 29. The other end of the secondary may be connected to a biasing battery 30, the positive side of which may be connected to the midpoint of a resistance 3| which may be connected between the line wires 2| and 22 by means of wires 32 and 33 respectively. Filtering condensers 34 and 35 may also be connected between the positive side of the battery 30 and the ends of the resistance 3|. The primary 36 of the transformer 29 may be connected to the output of an amplifier or other signal source. When an incoming signal is impressed on the primary 36 of the transformer 29 it afiects the secondary 28 and varies the potential on the modulating grid I9 which can never become positive due to the biasing battery 30.

When the current is turned on current flows through the wires 2| and 22, through the support rods 15 and I4, and through the refractory metal coil I 2 thereby raising the temperature thereof sufficiently to cause it to emit electrons as described in theabove mentioned copending application. The pressure of the gas in the envelope in and the voltage across the filament I2 is sufficient to cause an ionic discharge extending out from the filament and lengthwise thereof. This discharge appears along the filament like a halo and is intensely bright, giving an intense weight illumination.

When the charge on the modulating grid is negative the tendency is to cause the halo formed around the filament to draw in upon the filament and when the grid is charged positively it tends to pull the halo out from the filament increasing its cross-sectional area. In other words, as the potential of the modulated grid is varied the halo around the filament expands and contracts thus varying the intensity of the light produced. Inasmuch as the electron emission from the coated filament is easily controlled by the slightest potential change of the modulating grid the ionization of the gas is as easily controlled as it depends on the electron emission from the filament and hence the light is caused to vary in accordance with the modulation of potential upon the grid.

A suitable television apparatus as shown in Fig. 1 may be provided for using such a light to transmit an image electrically and project it upon a screen. In this apparatus the light from the lamp may be directed or converged by means of a lens 31 upon a scanning disc 38 which rotates in front of the lens and is provided with the usual series of holes formed in a spiral path so that the light projected through the disc is moved across the screen in successive horizontal lines. A suitable lens' system 40 may be provided to converge or project the image of the hole in the scanning disc upon a screen 4|. When the primary 36 of the transformer 29 is suitably connected to a lightsensitive cell exposed to light reflected from an object' through a scanning disc similar to that shown at 39 and rotating in synchrony therewith, the object will be reproduced upon the screen 4|.

In Fig. 2 I have shown a system whereby the lamp may be used for recording sound on a moving picture or other type of film. Here the lamp and circuit are exactly similar to what has been shown in Fig. 1 but in place of the scanning disc an aperture plate 42 is shown having an aperture 43 against which the light is directed by means of the lens 31, the lens system 44 being used to project a picture of the lighted aperture 43 upon the film M which is caused to move at a uniform rate in the plane upon which the light is focused. When a microphone or other apparatus for translating sound into electrical impulses is suitably connected to the primary 36 of the transformer 29 an accurate record of the sound is produced on the sensitive surface of the film. I

In some instances it may be desired to use the lamp as a signal light as for instance for ship to ship signaling in which case the light is modulated in accordance with a telegraph and due to the nature of the light produced may be read at considerable distance by any one familar with the code who can see the light. In such a signaling system the construction of Fig. 3 may be used. In this diagram the connections for the lamp are the same as in the preceding figures with the exception that a telegraph key M5 is used in place of the transformer 29 so that the key is connected between the wire it which forms the lead for the modulating grid and the biasing battery 30. Depressing the key lt places a negative charge upon the control grid of the light and causes the discharge halo to contract more closely against the filament with the result that the light is cut down while as soon as the circuit is opened by releasing the key M this negative potential is removed from the control grid and the discharge halo immediately increases thereby increasing the light intensity. Heretofore it has been impossible to find a lamp which can be used for this purpose due to the thermal lag in present day lamps which is too great to transmit modulation even as slow as a telegraph code. Such signaling has been accomplished by the use of movable shutters to control the light in accordance with the dot and dashes of the code. With the present invention, however, the circuit is greatly simplified doing away with all mechanical devices and due to the light intensity of the light produced the light can be seen very much further than anything which is now in use.

The lamp may also be used successfully wherever modulated light is desired, as for instance in advertising, to provide an intermittently flashing sign.

While the invention has been described particularly in connection with an electric light it is to be understood that it is applicable under any conditions where an ionic discharge is desired to be controlled by varying the potential on an adjacent electrode.

Many modifications of the invention may be resorted to without departing from the spirit thereof, and I do not desire to limit the invention therefore except as such limitations occur in the appended claims.

What I claim is:

1. An electron discharge device comprising a member capable of emitting electrons when heated, an inert ionizable gas surrounding said member, said gas being at such a pressure that a luminous discharge takes place along the element when a potential is impressed on the element which brings the temperature thereof to the point of profuse electron emission and which exceeds the breakdown potential of the ionized gas, and means adjacent said element for controlling the discharge from said element,

2. An electron discharge device comprising an envelope, a filamentary conductor within said envelope, an electron emitting coating on said conductor, an ionizable gas surrounding said conductor, the pressure of said gas being sufficient to restrict the densely ionized portion of said gas to the vicinity of said electron emitting coating when said coating is raised to electron emitting temperature and the potential drop along the conductor exceeds that of the ionized gas layer, and a control conductor in the vicinity of said filamentary conductor.

3. An electrical discharge device comprising an envelope, a filamentary conductor within said envelope, an electron emitting coating on said conductor, a mixture of neon and argon gas surrounding said conductor within said envelope, the pressure of said gas being sufiicient to confine the densely ionized portion thereof to the vicinity of said conductor when said conductor is raised to an electron emitting temperature and the potential drop along the conductor exceeds that of the ionized gas layer, and a control conductor in the vicinity of said filamentary conductor.

4. An electric lamp comprising an envelope, a filamentary conductor within said envelope wound in the form of a helix, a coating of electron emitting material on said conductor, and an ionizable gas within said envelope, and having a pressure such that the dense ionization of said gas is confined to the vicinity of a portion of said conductor in a tubular sheath surrounding said conductor, and a control conductor in the vicinity of said first mentioned conductor, said control conductor including a support rod and a plurality of rings surrounding said filamentary conductor. 5. In a device of the class described an elongated electron emitting element, an ionizable gas surrounding said element said gas having a pressure suficient to confine the ionization thereof to the vicinity of said element, and a plurality of wire loops surrounding said element and connected electrically together.

SL RUBEN. 

